Blades for tire curing molds are well known in the art of tire manufacture. Such blades are conventionally made from a running length or strip of a metallic material such as steel, stainless steel or brass. The strip is generally about 0.020 inches (0.5 mm) to 0.040 inches (1 mm) thick and has a width of about one half to 11/2 inches. Sometimes the strips are of solid form other times perforated strips are used to form the blade.
In U.S. Pat. No. 3,880,020 a method and apparatus for making blades is disclosed which enables small quantity lots of a multiplicity of different styles of blades to be made rapidly and economically. The method and apparatus permits blades to be blanked out from the stack of material by a plurality of punch and die sets while the stock remains securely attached to an endless loop carrier. The invention uses a plurality of suppresses for forming bends in the blade if desired.
In U.S. Pat. No. 3,581,535 a similar method and apparatus for making blades is disclosed. The method and apparatus for making blades for use in tire molds includes piercing, notching, bending or otherwise altering the shape of a free end of strip material by successively positioning the free end and a plurality of shape altering tools in operative engagement and cutting off the formed blade from the free end.
The reader can appreciate or visualize finished blades of a given style falling into a large box after being formed and cut from the strip of blade stock.
The complexity of this automated blade forming apparatus make it abundantly clear that the formed blade must be rather simple in construction as shown in the appended prior art FIGS. 8 through 13. Bends, cuts, notches and holes are possible. What has not been possible to date was the employment of more complex shapes or varying the thickness of the blade at a specific location.
In French Patent 2,137,309 and U.S. Pat. No. 2,736,924 the features found in the preamble of claim 1 is shown.
The blade creates a sipe, which is a narrow groove or incision in the tread. The lateral ends of the blade, even if polished or ground round is a subsequent deburring operations, are sufficiently narrow to initiate crack propagation at this highly stressed region of tread.
To avoid this problem it has been an objective of the present invention to create blade ends and blade bends that are effective at stress relieving the tread elements adjacent the resultant sipe.